Nuclear fuel recycling is a mechanism of recovering un-split uranium and newly generated plutonium as energy source from fuel (spent fuel) used in the nuclear power plant. About 95% of spent fuel for nuclear power generation can be reused. Spent fuel is stored in the storage pool to lower the temperature and lower the radioactivity.
Spent fuel is cooled and stored in the storage pool to weaken the radioactivity. After
sufficient radiation activity is lowered, the spent fuel assembly is cut down into the size of about 3-4 cm. Then, dissolve the
fuel part with nitric acid and separate it into uranium, plutonium and fission products. The
uranium solution and plutonium solution are purified and denitrated to form uranium oxide
and uranium-plutonium mixed oxide. Waste liquid containing fission products has strong
radioactivity, so it is mixed with glass raw materials to be vitrified solids. In Japan, we strive
to steadily promote nuclear fuel cycle as basic policy of nuclear policy in order to make effective
use of resources and make energy more stable in the future. In addition to save resources,
it becomes "pure domestically produced energy resources", which has great significance for
Japan with low energy resources.
1, excavation from uranium mine
About 0.7% of uranium is uranium 235 which is prone to nuclear fission is contained, and about 23% of
uranium 238 which is hard to fission is included in about 99.2%.
2.smelting → conversion → concentration (to increase the concentration of uranium 235 to
3% to 5%) → re-conversion → molding processing → processing into fuel assemblies
By adjusting the number of neutrons that appeared at the time of nuclear fission and filling
it for uranium 235 one after another, it is possible to stabilize the fission reaction. This is
called criticality.
3, introduction of reactor, start of power generation
Fuel in nuclear reactor is used for power generation for about three years and it is taken out after use. This is
spent fuel.The spent fuel contains about 95% of uranium 235, uranium 238, and newly
generated plutonium 239 which are remained from nuclear fission.
4, reprocessing
The above uranium and plutonium are recovered in the form of reprocessing and are called mixed oxide fuel (MOX fuel, Mixed Oxide Fuel). Then it will be used again in nuclear power plant - called “pluthermal” in Japanese.